Garden tiller with extended drag shield

ABSTRACT

A walk-behind garden tiller having power driven ground wheels and a single row of tines which are driven at relatively high speed in a direction counter to that of the drive wheels, whereby the tines cut upwardly through the untilled soil at the working face with less power and in the event of contacting an obstruction tend to move the machine in a rearward direction be reason of reactive forces acting upon the machine through the tines. A drag shield is pivotably mounted rearwardly of the machine for dragging along and smoothing the soil after it is tilled and for providing a protective barrier between the operator and a rear exposure to the power driven tines. The drag shield has a length greater than the vertical distance between its point of mounting on the machine and the bottom peripheral level of the tines and, in the event of sudden rearward movement of the machine during tilling, is adapted to anchor in the soil and thereupon be pivoted about such anchor point to elevate the rear of the machine, reducing tine contact with the soil and any obstruction.

DESCRIPTION OF THE INVENTION

The present invention relates to power operated soil tilling machines,and more particularly, to soil tilling machines of the type that aremanually manipulated and controlled by a person walking with or behindthe machine.

Manually operated soil tilling machines of the type which are intendedfor garden usage commonly comprise a frame having driven ground wheelsand a single row of power driven tines for penetrating and pulverizingthe earth. The tine shaft of such manually operated tilling machinestypically is driven in the same rotary direction as the ground wheelssuch that upon forward movement of the machine the tines willsuccessively contact the top of the ground and penetrate successivelayers of earth in the direction of machine movement.

Such conventional single tine shaft tilling machines frequently aredifficult for the operator to manipulate and control and sometimes cancreate dangerous situations, particularly when tilling very hard groundor soil which includes significant foreign materials or obstructions.Because the tines are rotating in the same direction as the groundwheels, when an obstruction is contacted, the tines tend to hook ontothe obstruction, lunge forward and continue running forward, in effect,climbing out of the ground from their tilling depth. Moreover, becausethe tines in such conventional tilling machines engage the top of thesoil, and in effect compress it during penetration, considerable poweris expended during tilling. Since power capabilities usually are limitedin walk-behind type tilling machines, such machines often incurdifficulties in effectively penetrating and tilling hard ground andother adverse soil conditions to a normal tilling depth in a single passof the machine.

It is an object of the present invention to provide a manually operated,walk-behind, type soil tilling machine that is capable of easier, saferand more effective usage, and is particularly adapted for operating inadverse soil conditions.

Another object is to provide a tilling machine as characterized abovewhich includes a rear mounted drag shield for smoothing the top of soilafter it is tilled and for more effectively providing a protectivebarrier between the operator and the rear exposure to the power driventines.

A further object is to provide a tilling machine of the above kindwhich, in the event the tines contact an obstruction, tends to movebackwardly a slight distance such that the operator is able totransverse the obstruction and maintain control of the machine withrelative ease.

Still another object is to provide a tilling machine of the foregoingtype which, in the event of sudden rearward movement of the machine byvirture of the tines contacting an obstruction, the drag shield thereofwill anchor in the soil and thereupon tend to elevate the rear of themachine, thereby reducing or eliminating the tine engagement with theground and the obstruction.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

FIG. 1 is a perspective of an illustrative soil tilling machineembodying the present invention;

FIG. 2 is an enlarged side elevation view of the illustrated tillingmachine;

FIG. 3 is an enlarged top view of the illustrated machine;

FIG. 4 is an enlarged fragmentary section taken axially through thesingle tine shaft of the illustrated machine;

FIGS. 5 and 6 are vertical sections taken in the planes of lines 5--5and 6--6, respectively, in FIG. 4;

FIG. 7 is an enlarged view of one of the tines of the illustratedmachine;

FIG. 8 is a plan view of the tip of the tine shown in FIG. 7 taken inthe plane of line 8--8 ;

FIG. 9 is a section of the tine shown in FIG. 7 taken in the plane ofline 9--9;

FIG. 10 is a diagrammatic illustration of the soil penetrating andcutting action of one of the tines of the illustrated machine;

FIG. 11 is a vertical section through the tine drive shaft and tineshield illustrating tilling during normal operating conditions;

FIG. 12 is a vertical section, similar to FIG. 11, but illustrating theaction of the machine upon contact with an obstruction;

FIG. 13 is a plan view of the extended drag shield of the machine takenin the plane of line 13--13 in FIG. 11;

FIG. 14 is a vertical section through the tine drive shaft showing theoperation of the machine when engaging long vegetation and illustratingthe action of a divider shield or sloughing member of the machine uponsuch vegetation;

FIG. 15 is a fragmentary section taken in the plane of line 15-15 inFIG. 14; and

FIG. 16 is a vertical section, generally similar to FIG. 14, but showingan alternative form of divider shield or sloughing member.

While the invention is susceptible of various modifications andalternative constructions, a certain illustrated embodiment thereof hasbeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed, but on the contrary, theinvention is to cover all modifications, alternative constructions andequivalents falling within the spirit and scope of the invention.

Referring now more particularly to the drawings, there is shown inillustrative soil tilling machine 10 embodying the present invention.The illustrated tilling machine 10 includes an elongated frame 11supported for rolling movement by a pair of ground wheels 12, a singlerow of ground penetrating and pulverizing tines 15 mounted on a tineaxle or shaft 18 located rearwardly of the ground wheels 12 andtransversely to the line of machine movement, an internal combustionengine 20 mounted on a forwardmost end of the frame 11 for rotatablydriving the ground wheels 12 and tines 15, and a vertically andtransversely pivotable handle 21 extending rearwardly of the frame 11for enabling a user to operate the machine while walking from behind oreither side. The machine 10 in this instance includes a hood 24pivotably mounted at 25 to permit access to the engine, a transmissionand body cover 26 located below and generally rearwardly of the hood 24,and a tine shield 27 located below the rearward end portion of thetransmission and body cover 26.

The machine frame 11 comprises a pair of transversely spaced, generallyhorizontally disposed supports 11a between which are mounted a groundwheel transmission 30 and a tine transmission 31 which serve to supportthe respective ground wheels 12 and tines 15 in depending fashion belowthe frame 11 and transmit power thereto from the engine 20, as bestshown in FIGS. 2 and 3. The engine 20, which typically may by afour-cycle gasoline powered internal combustion of between about fiveand eight horsepower, is mounted on the forwardmost end of the framesupports 11a. The ground wheel transmission 30 includes a two-partsealed housing 30a secured together by bolts 36. The transmission 30 hasan input shaft 38 rotatably carried in an upward portion of the housing30a above the frame 11 and a ground wheel axle 40 carried in a lowerportion of the transmission housing below the frame. The input shaft 38is coupled to an output shaft 45 of the engine 20 by respective sheaves46, 48 and a drive belt 49. It will be understood that the transmission30 may be of a known type which permits selective driving of the groundwheels at one or more forward speeds, or in a reverse direction, whenthe transmission input shaft 38 is driven by the engine. Thus, theengine 20 is adapted to power the ground wheels 12 through thetransmission 30 to move the machine 10 along a track that is to betilled by the tines 15.

In keeping with the invention, the tines are driven at a relatively highspeed in a direction counter to that of the ground wheels such thatduring normal forward movement of the machine during tilling the tinespenetrate and cut upwardly through the untilled soil at the working facein relatively shallow discrete layers and with substantially reducedpower requirements than heretofore necessary for conventional tillingmachines that operate in a downwardly directed ground engaging manner.In the illustrated embodiment, power is transmitted to the tine axle 18through the tine transmission 31, which like the ground wheeltransmission 30, comprises a two-part sealed housing 31a securedtogether by bolts 55. An upper portion of the transmission housing 31ais mounted between the frame supports 11a by bolts 56, and a lowerportion of the housing 31a extends below the frame supports 11a androtatably carries the tine axle 18.

For driving the tine transmission 31, as best shown in FIGS. 2 and 4,the housing 31a carries a rotatable input shaft 60 which is operativelyconnected to the input shaft 38 of the ground wheel transmission bymeans of a sheave 61 mounted on the tine transmission input shaft 60, abelt 64, and a sheave 62 mounted on the ground wheel transmission inputshaft 38. Input shaft 60 for the tine transmission 31 carries a pinion66, disposed within the transmission housing 31a, which drives a gear 68on an intermediate tine transmission shaft 69 rotatably carried by thehousing 31a. The intermediate shaft 69 is operatively connected to thetine axle 18 through a sprocket driven chain 71.

By virtue of such power transmission arrangement, with both the wheeland tine transmissions 30, 31 operatively engaged, when the engine 20drives the ground wheel transmission input shaft 38 in one direction,the wheel axle 40 and tine transmission input shaft 60 are driven in thesame rotary direction, while the intermediate tine transmission shaft 69and tine axle 18 are driven in an opposite rotary direction.Accordingly, when the tilling machine is driven in a forward operatingdirection, the wheels 12 rotate in a clockwise direction, as viewed inFIG. 2, while the tines are rotated in an opposite counterclockwisedirection. It will be understood by one skilled in the art that therelative rotary speeds of the ground wheel and tine axles 40, 18, andthus the peripheral speeds of the ground wheels 12 and tines 15, can beselectively established for a given engine output r.p.m. by appropriatedesign of the drive train and transmissions.

To permit selective engagement and disengagement of the tine and theground wheel transmissions 30, 31 with the engine 20, a clutch 85 isprovided, as shown in FIG. 2. The clutch 85 includes a bell crank 86that is pivotably mounted on the machine frame at 88 and carries anidler pulley 89 at one end thereof for engagement with the belt 49connecting the engine drive shaft 45 and the input shaft 38 for theground wheel transmission 30. The bell crank 86 is biased toward aclutch disengaging position in which the idler pulley 89 is disengagedfrom the belt 49 by a spring 87 extending between the pinion carryingend of the bell crank 86 and the machine frame. A clutch cable 90extends from another end of the bell crank 86 to a clutch lever 91(shown in FIG. 1) pivotably connected to the underside of the handle 21for easy access by the operator. By moving the clutch lever 91 in adirection toward the underside of the handle 21, the clutch cable willpivot the bell crank against the biasing force of the spring 87 in acounterclockwise direction, as viewed in FIG. 2, causing the idlerpulley 89 to be moved to a position tightening the drive belt 49sufficiently to drive the ground wheel transmission input shaft 38, andthus the tine transmission input shaft 60 connected thereto through thebelt 64. Upon release of the clutch lever 91, whether intentionally orin the event that an operator should stumble or otherwise lose controlof the machine, the bell crank 86 will be pivoted, under the biasingforce of the spring 87, to a position disengaging the idler pulley 89from tightening relationship with belt 49, thereby interrupting thedrive to the ground wheels and tines.

In order to permit selective disengagement of the tine transmission 31,while the ground wheel transmission 30 continues to be driven by theengine 20, a separate tine transmission clutch 95 is provided, as alsoshown in FIG. 2. The tine transmission clutch 95 includes a bell crank96 that is pivotably mounted on the machine frame at 98 and carries anidler pulley 99 for engagement with the belt 64 coupled between theinput shafts 38 and 60 for the ground wheel and tine transmissions 30,31, respectively. For selectively pivoting the bell crank 96, a clutchrod 100 is connected between the bell crank 96 and an over center clutchactuating handle 101 through a spring loaded connection 102. By pivotalmovement of a tine transmission clutch handle 101 in a clockwisedirection, as viewed in FIG. 2, it can be moved beyond a center positionwhich causes counterclockwise pivoting of the bell crank 96 moving theidler pulley 99 into a belt tensioning and clutch engaging position. Fordisengaging the clutch, the handle 101 is moved in a counterclockwisedirection, as viewed in FIG. 2, beyond its center position and pivotsthe bell crank 96 in a clockwise direction, relieving the tension on thedrive belt 64 and interrupting the drive to the tine transmission inputshaft 60.

Mounted upon the tine axle 18 on opposed sides of the tine transmissionhousing 31a in the illustrated machine, as best shown in FIGS. 4-10, aresimilar tine assemblies 110, each including three axially spaced pairsof 180° out-of-phase tines 15, each pair being 60° out-of-phase from theother pairs. The tines 15 of each pair are secured to a respectivetransverse tine plate 111 mounted on a tine assembly hub 112, which inturn is fitted over the respective end of the tine axle 18 and securedto the axle by a pin 114. The tines 15 preferably are of a hoeing type,each having a base portion 118 that is curved in a retreating oropposite direction to that in which the tine assembly is rotated and atip portion 119 that is bent laterally to the base portion 118 at thedistal end thereof. The tip portion 119 of each tine in this case has agenerally tapered portion 117 forming the leading cutting edge of thetine.

The illustrated tine assemblies 110, as shown in FIG. 4, each include apair of outermost tines 15a secured at their base 118 to an outer tineplate 111a by bolts 120a such that the tip portions 119 are directedlaterally inwardly, a pair of intermediate tines 15b secured to anintermediate base plate 111b by bolts 120b with the cutting tips thereofdirected laterally outwardly, and a pair of innermost tines 15c alsosecured to the tine plate 111b by bolts 120c such that the tip portionsthereof are disposed laterally inwardly. It will be appreciated thatbecause the intermediate and innermost tines 15b, 15c of each assembly110 are mounted on the same base plate 111b, they in effect form andoperate as a single four-tang tine, and alternatively, such a tine couldbe employed. For balancing the reaction forces on the tine axle 18during tilling, the tine assemblies 110 are similarly positioned on theopposed ends of the tine axle such that the outermost tines 15asimultaneously contact the soil, as do the intermediate tines 15b andthe innermost tines 15c.

The tine assemblies 110 preferably are supported by the tinetransmission housing 31 such that the depth of tine penetration duringnormal tilling (i.e.--with the machine frame 11 horizontally oriented)is between about three inches and five inches depending upon thehorsepower capability of the machine. In practice, it has been foundthat with a six-horsepower tilling machine embodying the inventionefficient tilling is obtained with tines having an effective cutting tipdiameter of 12" and disposed such that they project about 3" below thelowermost level of the ground wheels when the machine frame 11 is in itsnormal horizontal position. In an eight-horsepower tilling machine withtines having a cutting tip diameter of 14" efficient tilling has beenachieved with the tines disposed for a normal cutting depth of about 4"below the lowermost level of the ground wheels.

To permit selective adjustment in the vertical position of the rear ofthe machine frame during tilling, and thus, depth to which soil istilled, a depth control guide 122 (shown in FIG. 2) is secured to therear of the machine frame for selective vertical adjustment. The guide122 has a glide plate 124 at its lower end that normally rests on thetop of the tilled soil so that the rear of the tiller is supported at apredetermined height for the desired depth of tine penetration.

With the tines driven in a rotary direction counter to that of theground wheels during tilling, as illustrated in FIG. 11, it can be seenthat as the machine moves forward, the tip portions 119 of the tines 15contact and penetrate the soil at the working face in an upward sweepingmotion that tends to lift and loosen the soil even before the cuttingand penetration is completed. In contrast, in conventional machines inwhich the tines are operated in an opposite downwardly directed soilpenetrating mode, the tines tend to compress and compact the soil duringthe downward shearing and penetrating movement of the cutting tips,which causes greater resistance to tine penetration and necessitatesgreater power requirements. Hence, in practice the illustrated tillingmachine with the counter-rotating tine movement has permitted improvedpower efficiency, with significantly greater quantities of soil beingtilled per unit of time for given power limitations.

Moreover, because of the upward and forward cutting action of the tines15, the reaction forces acting on the machine during tilling aregenerally downwardly and rearwardly directed. As a result, during normaltilling operations, when the tines engage harder soil conditions, thetines tend to dig more aggressively and to move slightly rearwardly soas to reduce the depth of the cut, thereby enabling the operator tomaintain control of the machine with relative ease. It will beunderstood, however, that if the ground wheel drive is geared to pullthe machine forward faster than earth can be effectively penetrated infront of the tines, slippage of the power driven ground wheels willoccur, resulting in wasted energy and lower power efficiency, and insome instances, also causing the ground wheels to dig down or creep tothe side, hampering the handling ability of the machine. On the otherhand, if forward movement of the machine is too slow, the tines will bedigging less dirt than ideal, and hence, also reducing efficiency.

The tines preferably are driven at a relatively high speed, as comparedto conventional tilling machines, during normal forward tilling movementof the machine such that relatively thin, but yet discreet, layers ofearth are penetrated and severed during each upward passage of a tineacross the working face of the soil. More particularly, in practice,optimum effectiveness and efficiency has been achieved when the tineperipheral speed is at least eleven times the ground speed, andpreferably, when the ratio of such tine peripheral speed and groundspeed is within the range of about 11 to about 15 and most preferablywhen the ratio is at least 12. It will be understood that suchrelationship between the tine speed and ground speed is during low gear,forward movement of the ground wheels since tilling is ordinarily donein the low gear, while high gear operation generally is used only forcultivating or transporting of the tiller.

In practice, effective tilling has been efficiently achieved in asix-horsepower tiller embodying the present invention having an engineoperating speed of 3400 r.p.m. which drives 16" diameter ground wheelsat 16 r.p.m. in low gear (i.e.--for a ground wheel peripheral speed of67' per minute) and which drives 12" diameter tines at 260 r.p.m.(i.e.--for a tine peripheral speed of 817' per minute). The ratio of thetine peripheral speed to ground wheel peripheral speed in such case is12.2. Similar effectiveness and efficiency in tilling has been achievedwith an eight-horsepower tiller having an engine operating speed of 3400r.p.m. which again drives 16" drive wheels at 16 r.p.m. (i.e.--for aground wheel peripheral speed of 67' per minute) and drives 14" diametertines at an r.p.m. of 260 (i.e.--for a tine peripheral speed of 953' perminute). The ratio of tine peripheral speed to ground peripheral speedin such eight-horsepower tiller is 14.2. Each of the foregoing machinesembodying the present invention were found to operate with significantlyimproved power efficiency, tilled greater quantities of soil per unit oftime, and tilled to greater depths in a single pass of the machine thanheretofore available with comparably powered single tine shaft tillers.

The tilling machine 10 further has been found to till more effectivelyand be easier to manipulate in adverse soil conditions, such as in hardor rocky ground. As illustrated in FIG. 12, when a tine 15 engages anobstruction, such as a rock 125, during tilling the tiller will tend tomove rearwardly a slight distance (from the phantom line to solid lineposition shown in FIG. 12), by virtue of the reactive forces acting onthe machine and then forward again due to the effect of the groundwheels until the next tine strikes the obstruction, whereupon the tillerwill again move back a small distance. Such vibratory action willcontinue until the obstruction is either removed by the tines or thetiller is stopped or otherwise traversed around the obstruction. Incontrast, in conventional tillers having tines that are rotated in adownwardly directed soil penetrating and cuttng mode, when the tines areunable to penetrate an obstruction or hard soil condition the tines tendto hook on to the obstruction and cause the tiller to lunge forward andcontinue to run forward, in effect, climbing out of the tilling trench.Thus, the tilling machine of the present invention with thecounter-rotating tines also has been found to be more easilycontrollable and safer to operate in such adverse soil conditions.

For protecting the operator from the tines and for providing asemi-enclosure for confining flying and turbulent soil during tilling,the tine shield 27 has a hood type configuration and is secured to theunderside of the frame 11 directly beneath the rear transmission andbody cover 26 such that it is in overlying relation to the tines 15. Thetine shield 27 includes opposed sides 128 and a top 129 formed with asuitable aperture through which the tine transmission housing 31extends. Vertically adjustable side panels 130 are provided in dependingfashion from the shield sides 128 to allow for selective positioning ofthe side panels in accordance with the depth of tilling desired. Topermit vertical adjustment of the side panels 130, the panels are formedwith vertically disposed elongated slots 131 and are secured to theshield sides 128 by appropriate fasteners 132 passing through the slots.

For further enhancing pulverization of the tilled soil, the tine shield27 has a forward extension 27a which defines a cavity or space in frontof the tines to allow partially pulverized dirt directed upwardly by thecounter rotating tines 15 to accumulate in a small mound so that is canbe re-worked and more thoroughly pulverized as the machine proceedsalong its forward movement. To facilite the direction of flying dirtstriking the shield extension 27a onto such mound in front of the tines,the tine shield extension 27a terminates in a forwardly and downwardlydirected lip 27b. The top 129 of tine shield 27 in this case has astepped configuration comprising a first substantially flat horizontalpanel 129a above the tines, a second substantially flat horizontal panel129b which forms part of the shield extension 27a and is disposed at alower level than the first horizontal panel 129a, and an inclined panel129c interconnecting the first and second horizontal panels. The lip 27bof the forward tine shield extension 27a extends downwardly andforwardly from the lower forward, horizontal panel 129b, while a rearlip or panel 129d extends downwardly and rearwardly of the horizontalpanel 129a. The bends in the shield top 129 which define the severalpanels and lips preferably should be smoothly curved on the undersidethereof so as to resist undesirable buildup of dirt in the interiorcorners of the shield. The tine shield 27 in this case is mounted withthe stepped panels 129a, 129b, and 129c adjacent a similarly shapedvertical offset rear section 11b of the machine frame 11.

It will be appreciated that the shield extension 27a should extendforwardly and downwardly a sufficient distance so that it blocks mostforwardly directed dirt during tilling, but yet be high enough above theground to prevent dirt from building up below the shield and in effectthe plugging of the machine. Preferably, the forward extension 27a ofthe tine shield 27 extends forwardly of the front periphery of the tinesa distance "L" equal to about one-half the diameter of the tines anddownwardly to a level of about one-third the tine diameter below the topperiphery of the tines. It has been found that most forwardly andupwardly directed flying dirt will be blocked or appropriately directedby the tine shield extension if a lower leading edge 27d of the lip 27blies in a plane "P" that is tangent to the outer periphery of the tinesand at an angle preferably of about 40° to the horizontal, but in noevent, greater than 55° to the horizontal, as depicted in FIG. 11. Thelower leading edge 27d of the tine shield extension lip 27b alsopreferably should not extend below the level of the axle 40 of theground wheels 12 so that soil, vegetation, or other trash which passunder the ground wheel axle 40 will also pass under the leading edge ofthe shield 27. In practice, effective shielding and soil pulverizationhas been achieved in a tiller having 14" diameter tines with the tineshield 27 having an extension 27a extending a distance "L" of six inchesforwardly of the front periphery of the tines 15, a horizontal extensionpanel 129b disposed about one inch below the top peripheral level of thetines, and a forward lip 27b disposed at an angle of 60° below thehorizontal with the leading edge 27d thereof located 3" below the toppheriphery of the tines.

The effectiveness of such shield extension 27a during tilling is bestillustrated in FIG. 11, where it can be seen that by virtue of thecounter-rotating movement of the tines dirt is thrown upwardly in frontof the tines with a portion dropping downwardly into the rotating tineswhere it is further pulverized, a portion is directed rearwardly of thetines, and a portion is directed upwardly and forwardly of the tines.The shield extension 27a tends to block the forwardly sprayed dirt withthe lip 27b directing it onto a mound 135 of partially pulverized dirtimmediately in front of the power driven tines 15. As the machineprogresses in its forward movement, the tines will then re-work andfurther pulverize this mound 135 while continuing to form and accumulatea similar mound of partially pulverized dirt under the shield extension27a directly in front of the power driven tines.

For the purpose of cutting and breaking down long vegetation that mightexist on or in the ground being tilled and to prevent such vegetationfrom accumulating about the tine transmission housing or entanglingabout the rotary hub of the tine assemblies 110, a sloughing member 140is mounted forwardly of the tines between the lower portion of the tinetransmission housing 31a and the lip 27b of the tine shield extension27a, as illustrated in FIGS. 14 and 15. The sloughing member 140 in thiscase consists of a flat plate mounted in a vertical plane on thelongitudinal axis of the machine forwardly of the tine transmissionhousing 31a. One end of the plate 140 is secured to the tinetransmission housing 31a by the transmission housing bolts 55 and theother end of the plate is formed with a flange 141 that is bolted to theunderside of the tine shield lip 27b.

By virtue of the counter-rotating movement of the tines, it can be seenin FIGS. 14 and 15 that long vegetation 144, such as weeds, stalks, orthe like, will be swept upwardly by the tines 15 during tilling. As thetines lift such vegetation into contact with the sloughing plate 140,the sloughing plate will tend to either cut the vegetation into smallerlengths or guide the vegetation downwardly and around the bottom of thetransmission housing 131. In either case, the sloughing plate 140prevents the vegetation from wrapping around the tine shaft orexcessively accumulating around the transmission housing so as tootherwise impede effective tilling by the tines. With the longvegetation cut or broken down in size in such manner, it can then bemore readily mixed and dispersed in the tilled soil.

An alternative form of sloughing means is illustrated in FIG. 16 andincludes a disc 145 rotatably mounted in forwardly extended relation tothe lower end of the transmission housing 31a. The illustrated disc 145is mounted on a bracket 146 secured to the transmission housing by thetransmission housing bolts 55. The disc 145 preferably should bedisposed such that the lower periphery of the disc is located at or nearthe lower level of the transmission housing. During tilling, thesloughing disc 145 will function essentially the same as the plate 140previously described by cutting or breaking down long vegetation whichis carried upwardly by the tines into contact with the sloughing disc,as well as guiding such vegetation under and around the transmissionhousing 31a so as to prevent undesirable buildup or clogging of thetines.

For smoothing out the soil after it is tilled and for protecting thefeet of an operator walking behind the machine from injury by the powerdriven tines, a drag shield 150 (FIGS. 11-13) is mounted on the rear ofthe machine and has a lower edge 151 that drags along the top of thetilled soil. The drag shield 150 in this instance is pivotably mountedon the rear panel 129d of the tine shield 27 by a hinge connection 152,and preferably, the ground engaging edge 151 is formed with a serratedconfiguration.

In accordance with the invention, for further protecting the operatorfrom injury and for enhancing controllability of the machine, the dragshield 150 has a length that is greater than the distance from its pointof attachment on the machine to the lower peripheral level of the tinessuch that in the event the tines strike an obstruction that causes themachine to move rearwardly, the lower edge of the drag shield willanchor in the soil and by a lever-type pivoting movement about suchanchor point will tend to raise the rear of the machine, therebyeliminating or reducing tine contact with the soil and the rearwardthrust of the machine. To this end, the illustrated drag shield 150 hasa lower portion 155 which is bent at an angle φ of about 150° such thatis rides at a substantial angle with the tilled soil as the drag plateis pulled along. Such lower drag plate portion 155 tends to enhanceraking and smoothing of the tilled soil, as well as insuring a firmanchor point in the event of sudden rearward machine movement.

Accordingly, if the tines engage an obstruction, as illustrated in FIG.12, the resulting rearward movement of the machine by virtue of thereactive forces acting on the tines tends to anchor the serrated loweredge 151 of the drag shield 150 in the ground and pivot the drag shield150 about such anchor point, with the hinge connection 152 permittingrelative pivotable movement between the drag shield and the machinebody. Since the drag shield 150 is longer than the distance between itshinged connection 152 with the machine and the lower peripheral level ofthe tines 15, such pivoted movement of drag shield 150 automaticallytends to raise the rear of the machine slightly, thereby reducing oreliminating the tine engagement with the ground and the obstruction.When the obstruction is dislodged or otherwise traversed, and the groundwheels proceed to move the machine forwardly, the drag shield 150 willpivot forwardly about the anchor point in the ground, allowing the tinesto resume their normal tilling depth. It will be apparent that at alltimes, whether during normal tilling or when the drag shield is anchoredand pivoted to a tine disabling position, that the drag shield providesa complete and effective barrier between the operator and rotatablydriven tines.

From the foregoing, it can be seen that the tilling machine of thepresent invention is adapted for easier and safer usage. The tillingmachine further operates with improved power efficiency, can be readilyand effectively operated in various adverse soil and vegetationconditions, and is capable of tilling and thoroughly pulverizing earthto a geater depth in a single pass than heretofore possible with usualpower limitations of walk-behind type tillers.

What is claimed is:
 1. A walk behind garden tiller comprising, incombination, a horizontal frame, a handle secured to said frame andprojecting rearwardly therefrom for manual guidance of the tiller, anengine mounted on said frame, a tine drive shaft extending transverselyto and journaled in a position adjacent said frame, said tine driveshaft having a set of soil penetrating and cutting tines securedthereto, a tine drive train coupled between said engine and said tinedrive shaft for rotatably driving said tines, a rigid drag shieldpivotably mounted rearwardly of said tiller for smoothing soil after itis tilled and for providing a protective barrier between the operatorand a rear exposure to said tines, said drag shield being pivotablymounted at a point on the tiller above the elevation of said tine shaftand having a length greater than the vertical distance between its pointof mounting on the tiller and the bottom peripheral level of said tines,said drag shield having a lower ground engaging portion that is formedsuch that during tilling it is dragged along the top of the soil at asubstantial angle to the ground level and during rearward tillermovement said lower ground engaging portion is adapted to anchor in thesoil to elevate the rear of the tiller about such anchor to reduce tinecontact with the soil, and said lower ground engaging portion having adownwardly directed terminal edge shaped to enhance its ability toanchor into the soil during rearward movement of the tiller and to rakeand smooth the tilled soil during forward movement of the tiller.
 2. Thetiller of claim 1 in which said lower drag shield portion is formed atan angle to an upper portion of said drag shield.
 3. The tiller of claim2 in which said drag shield lower portion is disposed at an angle ofabout 150° to the upper portion of said drag shield.
 4. The tiller ofclaim 3 in which said drag shield lower portion has a serratedground-engaging edge.
 5. The tiller of claim 1 including a tine shieldoverlying said tines, and said drag shield is pivotably mounted to therear of said tine shield and forms a rear extension thereof.
 6. Thetiller of said claim 1 in which said tine drive shaft is journaledadjacent one end of said frame, and including ground engaging drivewheels mounted adjacent the other end of said frame, and a wheel drivetrain for coupling the engine to the drive wheels to drive the tiller ina forward direction.
 7. The tiller of claim 6 in which said tine drivetrain is directed so that the tine drive shaft revolves counter to thedirection of the drive wheels whereby said face and in the event ofcontacting an obstruction tend to move the tiller in a rearwarddirection by reason of reactive forces acting upon the tiller throughthe tines, and said lower drag shield portion being adapted to anchor inthe soil in the event of rearward machine movement and thereupon bepivoted about such anchor point to elevate the rear of the machine,reducing tine contact with the soil and any obstruction.
 8. Awalk-behind garden tiller comprising, in combination, a horizontalframe, ground-engaging drive wheels mounted adjacent one end of theframe, a tine drive shaft extending transversely to and journalled in aposition adjacent the other end of the frame, an engine mounted on saidframe, a wheel drive train for coupling the engine to the drive wheelsto drive the tiller in the forward direction, a rearwardly projectinghandle secured to the frame for manual guidance of the tiller, said tinedrive shaft having a set of soil penetrating and cutting tines securedthereto, a tine drive train for coupling the engine to the tine driveshaft, said tine drive train is directed so that the tine drive shaftrevolves counter to the direction of the drive wheels whereby said tinescut upwardly through the untilled soil at the working face and in theevent of contacting an obstruction tend to move the tiller in a rearwarddirection by reason of reactive forces acting upon the machine throughthe tines, a drag shield pivotably mounted rearwardly of said tiller fordragging on and smoothing soil after it is tilled and for providing aprotective barrier between the operator and a rear exposure to saidtines, said drag shield having a length greater than the verticaldistance between its point of mounting on the tiller and the bottomperipheral level of said tines, said drag shield having a lower groundengaging portion that is formed such that during tilling it is draggedalong the top of the soil at a substantial angle to the ground level andduring rearward tiller movement said lower ground engaging portion isadapted to anchor in the soil to elevate the rear of the tiller aboutsuch anchor to reduct tine contact with the soil, and said lower groundengaging portion having a downwardly directed terminal edge shaped toenhance its ability to anchor into the soil during rearward movement ofthe tiller and to rake and smooth the tilled soil during forwardmovement of the tiller.
 9. The tiller of claim 8 in which said dragshield lower portion is formed at an angle to an upper portion of saiddrag shield.
 10. The tiller of claim 9 in which said drag shield lowerportion is disposed at an angle of about 150° to the upper portion ofsaid drag shield.